The present invention relates to a beat density detecting apparatus for detecting a beat density as characteristics of audio information, such as music and voices, and to an information playback apparatus equipped with the beat density detecting apparatus.
The present invention claims priority from Japanese Application No. 2001-149366, the disclosure of which is incorporated herein by reference for all purposes.
Conventionally, an information playback apparatus, such as a CD (Compact Disc) player and a DVD (Digital Versatile Disc) player, is provided with a spectrum display unit for displaying frequency characteristics of a playback sound played at a speaker.
The spectrum display unit is formed on a manipulation panel unit of the information playback apparatus, and as shown in FIG. 14, displays a spectrum obtained by subjecting audio data played back from a CD or a DVD to a Fourier transform and the like in real time as a level (unit: decibels) with respect to an audio frequency band.
Also, the manipulation panel unit of the information playback apparatus is provided with an equalizer adjustment unit accompanying the spectrum display unit, so that a user can adjust the frequency characteristics of a playback sound by properly adjusting the positions of a plurality of sliding adjustment levers provided to the equalizer adjustment unit.
Incidentally, according to the conventional information playback apparatus, a user can visually recognize a spectrum (frequency characteristics) of a playback sound in real time while listening to the playback sound from a speaker or a headphone. Hence, in general, even when the user cannot detect a spectrum of a playback sound clearly with his/her sense of hearing, he/she can detect the spectrum (frequency characteristics) easily with his/her sense of sight, which makes it possible to attain an advantage that the user can readily process a playback sound into a sound having desired equalizer characteristics superimposed thereon, by manipulating the equalizer adjustment unit as needed.
However, as shown in FIG. 14, the conventional spectrum display unit merely displays a spectrum of a playback sound currently being played at a speaker or a headphone. In other words, the conventional spectrum display unit displays only an instantaneous spectrum (frequency characteristics) of a playback sound as fluctuations of the level within the audio frequency band.
For this reason, even when the user wishes to know the whole of the characteristics of one song of music from start to end by playing a music CD, it is difficult to know the characteristics as a whole by looking at an instantaneous spectrum (frequency characteristics) of a playback sound.
To give a more concrete example, a song of music has a portion referred to as “chorus” to strongly stir emotions in people, an introduction portion provided to highlight the “chorus” portion, an ending portion to leave lingering tones. etc., and words and music are written to organically mix these various characteristics, so that the song emotionally appeals to the user. However, there is a problem that the user cannot know these various characteristics of music as a whole by merely looking at an instantaneous spectrum (frequency characteristics) of a playback sound.